青藏高原高寒草甸植被和土壤对短期禁牧的响应

为探讨青藏高原高寒草甸对短期禁牧的响应,设置冬季自由放牧和短期(2年)禁牧的对比试验。采用随机样方法调查植被群落盖度,分析地上和地下生物量、根冠比、植被地上和地下部分以及表层(0-10cm)土壤全碳、全氮和全磷含量、生态化学计量以及营养元素的关联性。研究结果显示:1)短期禁牧显著改变高寒草甸植被盖度、地上生物量、根冠比、植被全磷含量和N∶P,以及土壤全磷含量。2)相关性分析表明,禁牧后土壤全碳含量与植被地上全碳含量呈显著相关性,自由放牧后土壤全碳和全氮含量分别与植被地下部分全碳和全氮含量呈显著相关性。结果表明,不同的草原管理措施(禁牧、放牧)会改变高寒草甸植被与土壤养分分配及其平衡关系,同时,植被与表层土壤主要养分含量之间的关联性仅存在于部分植物器官与部分营养元素之间。

Responses of vegetation and soil of alpine meadows on the Qinghai-Tibet Plateau to short-term grazing prohibition

Because of the harsh climate and high altitude of the Qinghai-Tibetan Plateau (QTP), the Alpine Meadow, the dominant vegetation of the plateau, could easily degenerate due to overgrazing. This research study aimed to investigate the responses of vegetation and top-soil (0-10cm) to short-term grazing prohibition. We collected samples from a winter pasture enclosed for two years (short-time grazing prohibition) at the Zoige Wetland Ecosystem Research Station, Chinese Academy of Sciences, in Hongyuan County of the northeastern margin of QTP. The sample sites were randomly selected in the field, the community coverage was recorded, and the above ground (shoots) and below ground (roots) parts of the grass were collected and cut at the root collar. We weighed the shoot and root biomass; determined the root-shoot ratio (R/S); and measured the concentrations of total carbon (C), total nitrogen (N), and total phosphorus (P) of the vegetation and top-soil. In addition, the ecological stoichiometric linkages of the main nutrients (C, N and P) were analyzed. The main results were as follows. 1) Grazing prohibition significantly changed the vegetation coverage, aboveground biomass, R/S, P concentration in both vegetation and soil, and N:P of the vegetation. However, it had no significant effect on the below ground biomass, C and N concentration, C:N and C:P of the vegetation and soil, or N:P of the soil. 2) There was a significant relationship between the C concentration of the soil and that of the shoots under grazing prohibition conditions, and between the C and N concentration of the soil and those of the roots under grazing conditions. The results suggested that grassland management measures would change the distribution and balance of vegetation and soil nutrients of the Alpine Meadow, and the linkages of the main nutrients contents between the vegetation and top-soil in the Alpine Meadow exists in specific parts of the plant organs.